We take drinks and snacks too. Especially in the hotel for evenings.
We have been to train station shop a few times. I can't exactly remember what they have but it's the usual range of crisps, biscuits and other normal snacks. It's not that it's particularly cheap, it's just normal price for the normal world. But a lot cheaper than Disney snacks.
We do love having the occasional Disney snack but we worked out last time that for 5 people (all adults) to have a snack and drink (like a muffin and coke) it was about €30.
So I'd recommend tubbsys idea because even if you don't eat them all and have to bin some at the end it will still save more money.